brakes sinking to floor on own?

[9002GTgouge]

my brakes on my 02 gt have a mind of their own they sunk to the floor al by their selves all 4 are locked up fluid is full any ideas?

 

[ACSPONY]

Bad master cylinder keeping pressure?
I'd check the chapter on brakes in my auto tech book but I'm lazy...
EDIT:
I love this book...
"if the pedal drifts toward the floor and there is no visible sign of fluid leakage anywhere in the system, the master cylinder is leaking internally past the primary cup." Try pushing the brakes down to make the seal press against the wall of the cylinder to cut off the leak. Also check for fluid leaking either through the firewall or the front of the power booster.
~A.C.

 

[9002GTgouge]

thanks i ll check it out to see if any leaks. any thing about the hydroboost? maybe hooked up wrong also when engine is not running brakes seem fine or when serpintine belt is not hooked up